Process for liberating iodine in iodine-containing mineral waters



Patented Sept. 16, 1930 UNITED STATES PATENT OFFICE lFBITS ELLINGEB, 01: TEE HAGUE, NETHERLANDS, ASSIGNOB T MIJ'NBOUW EN EANDELSMAATSCHAPPIJ, WONOH GEDEH, OF THE HAGUE, NETHERLANDS PROCESS FOR LIBEBATING IODINE IN IODINE-CONTAINING WATERS No Drawing. Application filed March 7, 1929, Serial No. 345,229, and in the Netherlands March 10, 1928.

For obtaining iodine several methods are already known, including obtaining iodine and iodine compounds from iodine-contain-' ing' charcoal.

5 The present invention relates to a process for liberating iodine from its compounds in iodine-containing mineral waters, whilst the liberated iodine can then be adsorbed by charcoal.

It is known that many oxidizin agents are suitable for liberating iodine om iodides. In Abeggs Handbuch der Anorg. Ghemie Vol. IV, 2 (1913) page 348 it is stated that permanganic acid is specially suitable for separating iodine from iodides in order to obtain a particularly pure iodine.

This method has however never found commercial application, nor has it ever been proposed for liberating iodine from iodinecontaining mineral spring-waters, in which only very small quantities of iodides besides a large excess of other salts are present.

Until now, for liberating iodine from spring-waters only sodium nitrite in acid solution or nitric sulphuric acid has been used. These chemicals have been considered the most suitable for the object on account.

of their cheapness and it has never been proosed to use anything else. It has now been ound, however, that the use of nitrite as an oxidizing agent is not profitable; it has also been found that when using sodium nitrite, the reaction proceeds slowly and a large excess of nitrite and acid is needed in order to obtain the iodine almost quantita tively in reasonable time. Also most of the other oxidizing" agents do not come into consideration. Chlorine occasions formation of iodic acid, from which the iodine cannot be obtained by adsorption in carbon. Experi ments with iron chloride have showed that also here the separation takes place slowly, whereas the iron creates trouble, detrimental to the later adsorption. The solution filtered after the treatment still gives a distinct colouring with carbon disulphide, which shows that the iodine had not yet been Completely precipitated.

Experiments with potassium permanvanote however have showed that wi 11 the thesodium iodide) with a content 0 39.6 mg. I

iodine per liter are added 0.5 com. normal sulphuric acid plus the theoretical quantity of sodium nitrite and 10 ccm. carbon disulphide.

Within an hour the liberation of the iodine commences and increases slowly.

After 24 hours 40%of the iodine is separated.

After 48 hours60% of the iodine is separated. 7

After 5 days it can be proved, after addition of a new quantity of carbon disulphide, that the iodine is completely separated.

(2) To 100 ccm. of a perfectly neutralized iodinecontaining water, containing 10 mg. iodine as sodium iodide, 0.15 ccm. sodium nitrite (10% solution) and 0.2 ccm. normal sulphuric acid (theoretically 0.054 ccm. nitrite solution and 0.16 ccm. normal sulphuric acid wouldbe sufiicient) are added.

After 24 hours 6 mg. iodine or 60% is separated.

(3) To 100 com. iodine-containing water of the same composition as in experiment 2 are added 0.15 ccm. sodium nitrite and 0.5 ccm. normal sulphuric acid.

After ,1 hour 9 mg. iodine are now separated.

After 20 hours the complete separation of 10 mg. iodine is efiected.

(4) To 100 com. iodine-containing water of the same composition as in experiments 2 and 3 are added I .015 com. sodium nitrite and 2.5 ccm. normal sulphuric acid.

The separation of the iodinenow is instantaneous and complete.

(5) 100 com. iodine water as above is mixed with a solution of 2.5 mg. potassium permanganate and 0.2 ccm. normal sulphuric acid (theoretically required 2.5 mg. KMnO), and 0.13 ccm. normal H SO Here the iodinais liberated immediately and quantitatively. Also with less sulphuric acid this result is still obtained. In the treatment of 1 million liters iodine water per day the 5th experiment requires, as compared to the third, a smaller consumption of sulphuric acid of 150 kg. per day, which in the Dutch East Indies amounts to a saving of approximately $10. Further 10% more iodine is ob tained therewith, as it is technically.imprac-. ticable to spend 20hou rs on liberating th iodine, during which time also apart of the iodine'would doubtless be lost by evaporation.

The high cost of chemicals for the separation of iodine with sodium nitrite'and sulphuric acid is just the reason why people in Java have returned in many instances to the separation of iodine as cuprous iodide.

The present invention therefore effects an important saving in chemicals, as not only much less sulphuric acid is necessary but also so much less permanganate that the cost hereof is much less than the otherwise cheaper nitrite.

Furthermore the separation of the iodine takes place instantaneously and quantitative ly, so that one can commence immediately with the adsorbing of the liberated iodine by charcoal, without losing iodine by evaporation through long duration of the reaction, as can take place when the work is done with sulphuric acid and sodium nitrite and when working without a great excess of these chemicals, which excess is not economical and therefore often avoided. This latter case causes in practice a considerably smaller recovery of the iodine than the water originally contains.

In carrying outthe process the procedure is preferably as follows:

.method. The water, which is now only weakly alkaline, is-then' neutralized completely with sulphuric acid, for which only a little sulphuric acid is necessary. Then the neutral iodine-containing water is acidified with very little sulphuric acid, namely to a very weak acid reaction. Thereupon potas sium permanganate is added according to the invention, namely for every gram of io dine which the water contains, 0.25 g. potas-. sium permanganateis added. Only a very weak acid reaction of the iodine water is necessary andith'e potassium permanganate is then reduced directly to manganous salt without formation of manganese dioxide. The solution remains clear; no colloidal metall hydroxide formation takes place, which otherwise could work unfavourably on the' adsorption of the iodine by the charcoal. It is'also disadvantageous to take an excess of potassium permanganate, on account of the cost, as because, after the liberation of the iodine any possible organic compounds presout are oxidized, be it only slowly, by the dine-containing spring-waters which comprises neutralizing the spring-water, mixing it with an exceedingly smallquantity of acid and approximately the theoretical quantity of potassium permanganate and with an ad-' sorbing agent.

3. Process for'extracting iodine fromio dine-containing spring-waters which comprises neutralizing the spring-water, mixing it with an exceedingly small quantity of acid and approximately the theoretical quantity of potassium permanganate and with charcoal.

FRITS ELLINGER. 

